You've seen already this Battle Map in four languages at 14,95 euro?
Battle Map / Frontkaart / Carte du Front / Frontkarte 1914-1918 and it's web application? It covers only the Belgian part of the Western Front Zone but to be honest, if you want to see all of it, you need a few days at least!
If interested in staying close to canals and old railway tracks, this is a track that brings you from Comines/Wervik to Ypres, Veurne, Diksmuide and Nieuwpoort along the Yser, the Ieperlee Canal, the Palingbeek, the Nieuwpoort-Dunkirk Canal, the Lovaart and the railway track between Nieuwpoort and Diksmuide: http://www.bikely.com/maps/bike-path...rne-Nieuwpoort